The LG G5 phone supports DisplayPort 1.2 over the USB Type-C interface which should allow it to work with other external displays supporting DisplayPort.
Unfortunately, the LG G5 had problems connecting to the ASUS MB169C+ USB Type-C Portable Monitor using the USB 3.1 Type-C to Type-C cable that comes with the monitor.
Once the LG G5 was connected to the ASUS MB169C+ USB Type-C Portable Monitor, the phone automatically showed that it was ready to start charging the monitor. When initiated, the phone kept trying but was never able to connect or establish screen mirroring with the monitor. Regrettably we could not get DisplayPort to work between the LG G5 and the ASUS MB169C+ USB Type-C Portable Monitor.